Recent advances in molecular engineering and neuroscience have led to an increasing number of biomarkers and therapeutic agents for the monitoring and treatment of neurological disorders. Many of these agents have proven in vitro specificity or neurological potency, but their in vivo efficacy remains limited by their inability to reach their target due to the blood-brain barrier. This interface regulates the exchange of molecules across the cerebral capillaries through passive, transport, and metabolic barriers, resulting in the exclusion of nearly all agents larger than 400 Da from the brain's extracellular space. Biomarkers and therapeutic agents, such as inhibitors to enzymes (˜1 kDa) and antibodies (30 to 300 kDa), are thus rendered ineffective because they do not reach their intended targets.